The present invention relates to laser cutting machines that cut workpieces with laser beams. More particularly, the present invention relates to a laser cutting machine that automatically adjusts the laser beam focal point position relative to a workpiece surface.
A typical laser cutting machine has a laser head, and a torch unit attached to the laser unit. The torch unit has a nozzle through which a laser beam is emitted toward a workpiece to cut the workpiece.
The laser beam is converged at a certain focal point relative to the surface of the workpiece. The optimal position of the focal point depends on various factors such as the material and thickness of the workpiece. The focal point position of the laser beam relative to the workpiece surface is adjusted prior to the cutting of the workpiece. The adjustment is normally carried out by changing the distance between the distal end of the nozzle and the focal point of the laser beam. In the prior art, the adjustment of the focal point position is carried out manually using an adjustment mechanism provided in the torch unit.
Therefore, the adjustment of the focal point position is burdensome. Furthermore, the adjustment must be performed manually. This is disadvantageous when automating the cutting of workpieces. To overcome such shortcomings, a servo control mechanism installed in the laser head, or torch unit, has been proposed to automatically adjust the focal point position. However, in such structure, the torch unit is required to include an actuator, such as a motor. This not only complicates the structure of the laser head but also increases the size and weight of the laser head.